1. Field of the Invention
The present invention relates generally to a magnetic disc unit and more particularly to a magnetic disc unit of the type in which a motor drives a magnetic disc clamping mechanism for automatically clamping the magnetic disc and a magnetic disc releasing mechanism for automatically releasing the clamped magnetic disc.
2. Description of the Prior Art
For instance, when a magnetic disc is ejected from a magnetic disc unit while recording or reproducing due to an erroneous operation of the magnetic disc unit, erroneous data are recorded or a host system operation is interrupted.
Therefore, various safety devices have been proposed to prevent a magnetic disc eject mechanism from being actuated even when the magnetic disc is erroneously operated while it is recording or reproducing.
For instance, there has been used a mechanical safety mechanism which mechanically locks a door through which a magnetic disc is loaded into or ejected from a magnetic disc unit during the recording or reproduction mode. There has been also used a mechanical safety mechanism which locks a magnetic disc eject lever during the recording or reproduction mode.
Meanwhile, there has been proposed a magnetic disc unit in which upon insertion or loading of a magnetic disc into the magnetic unit, the magnetic disc is automatically clamped and upon depression of a magnetic disc eject button switch, the magnetic disc is automatically ejected from the magnetic disc unit (see, for instance, Japanese Patent Application Laid Open No. 177265/1982).
As described above in this unit, a magnetic disc is automatically clamped and ejected, so that the operability is improved and the centering accuracy of a magnetic disc is ensured. However, this automatic clamping and ejecting magnetic disc unit is not provided with a safety device which can protect a magnetic disc during the recording or reproduction mode when the magnetic disc unit is erroneously operated. As a result, when an eject button switch is depressed, for instance, a magnetic disc is automatically ejected from the magnetic disc unit, so that the data in the magnetic disc are destroyed.
Furthermore, since the clamped magnetic disc is automatically released and ejected only by depressing the eject button switch, the magnetic disc cannot be released and accordingly cannot be ejected from the magnetic disc unit in the case of breakdown or malfunction of a magnetic disc unit or a host system. In this case, there may be no problem when a magnetic disc is not clamped, but when the breakdown or malfunction occurs while the magnetic disc is clamped, the clamped magnetic disc cannot be ejected from the magnetic disc unit until such a breakdown or malfunction of the magnetic disc unit or host system is completely removed.